Byars disclosed a "Combined Tire Inflator and Pressure Gauge" in his U.S. Pat No. 2,047,405, which however has the following disadvantages:
1. The cup leather (his numeral 39) is too short to be stably reciprocated within the bore of gauge body (10). If such a cup leather (39) serving as a piston is made to be a longer "plunger", the gauge body (10) must be extended longer to allow the movement of the gauge rod (37) to cause inconvenience for its carriage. PA1 2. The spring (40) is retained by a washer (36) which is fixed within the body (10) and is therefore not adjustable in case of fatigue failure of the spring (40). PA1 3. If the spring (40) is made to be adjustable, the length of the spring must be so long enough to be across the bore of thebody (10), whereby the coils of the spring (40) will be visible through the window (32) to influence the reading of the pressure data as shown on the gauge rod (37).
The presnt inventor has found the defects of Byars' U.S. Pat. No. 2,047,405 and invented the present tire gauge.